The present invention relates to detection of rotation or angular deflection of a suspended object being connected with a reflector which turns with the object.
The detection of a deflection is used, for example, in torque measuring instruments. The U.S. Pat. No. 3,026,472, for example, describes a null type gas analyzer which has a very high sensitivity. The object being suspended by a torsion fiber in a dumbbell which experiences very small torque in magnetic fields and twists the fiber slightly. A reflector is affixed to the fiber, and light from a source is deflected in a direction that varies with any change in position of the reflector. A beam splitter divides the reflected beam in two portions which vary in intensity in opposite directions upon deflection of the reflector. Two photoelectric detectors respond to the two beams and a circuit forms a difference or error signal which is used to control electrically the torque exerted on the suspended object so as to restore the deflection to a null position in which the two beams balance. The control current needed to maintain that balance is a measure of the torque which tended to deflect the object.
The principles employed here are quite satisfactory. However, the construction is rather complicated and, therefore, readily amenable to interference requiring readjustment etc. Most particularly, the optical path (actually a dual path) is rather elaborately defined which complicates construction, adjustment positioning, handling, use, and maintenance.